Clomethiazole cimetidine

The serum levels of many of the benzodiazepines and related drugs are raised by cimetidine, but normally this appears to be of little or no clinical importance and only the occasional patient may experience an increase in the effects (sedation). The interactions with midazolam, zaleplon, and Zolpidem may be more significant, but this is not established. Famotidine, nizatidine and ranitidine do not normally appear to interact with most benzodiazepines. Increased sedation appears to occur with clomethiazole and cimetidine. 

Cimetidine increases plasma levels of zaleplon and slightly increases sleep duration with zolpidem. Cimetidine reduces the clearance of clomethiazole and increases sleep duration from a range of 30 to 60 minutes up to at least 2 hours. ... 

Cimetidine inhibits the liver enzymes concerned with the metabolism of diazepam, alprazolam, chlordiazepoxide, clomethiazole, clorazepate, flu-razepam, nitrazepam, triazolam, and zaleplon. As a result their clearance from the body is reduced and their serum levels rise. 

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